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Theorem onintexmid 4574
Description: If the intersection (infimum) of an inhabited class of ordinal numbers belongs to the class, excluded middle follows. The hypothesis would be provable given excluded middle. (Contributed by Mario Carneiro and Jim Kingdon, 29-Aug-2021.)
Hypothesis
Ref Expression
onintexmid.onint ((𝑦 ⊆ On ∧ ∃𝑥 𝑥𝑦) → 𝑦𝑦)
Assertion
Ref Expression
onintexmid (𝜑 ∨ ¬ 𝜑)
Distinct variable group:   𝑥,𝑦
Allowed substitution hints:   𝜑(𝑥,𝑦)

Proof of Theorem onintexmid
Dummy variables 𝑢 𝑣 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 prssi 3752 . . . . . 6 ((𝑢 ∈ On ∧ 𝑣 ∈ On) → {𝑢, 𝑣} ⊆ On)
2 prmg 3715 . . . . . . 7 (𝑢 ∈ On → ∃𝑥 𝑥 ∈ {𝑢, 𝑣})
32adantr 276 . . . . . 6 ((𝑢 ∈ On ∧ 𝑣 ∈ On) → ∃𝑥 𝑥 ∈ {𝑢, 𝑣})
4 zfpair2 4212 . . . . . . 7 {𝑢, 𝑣} ∈ V
5 sseq1 3180 . . . . . . . . 9 (𝑦 = {𝑢, 𝑣} → (𝑦 ⊆ On ↔ {𝑢, 𝑣} ⊆ On))
6 eleq2 2241 . . . . . . . . . 10 (𝑦 = {𝑢, 𝑣} → (𝑥𝑦𝑥 ∈ {𝑢, 𝑣}))
76exbidv 1825 . . . . . . . . 9 (𝑦 = {𝑢, 𝑣} → (∃𝑥 𝑥𝑦 ↔ ∃𝑥 𝑥 ∈ {𝑢, 𝑣}))
85, 7anbi12d 473 . . . . . . . 8 (𝑦 = {𝑢, 𝑣} → ((𝑦 ⊆ On ∧ ∃𝑥 𝑥𝑦) ↔ ({𝑢, 𝑣} ⊆ On ∧ ∃𝑥 𝑥 ∈ {𝑢, 𝑣})))
9 inteq 3849 . . . . . . . . 9 (𝑦 = {𝑢, 𝑣} → 𝑦 = {𝑢, 𝑣})
10 id 19 . . . . . . . . 9 (𝑦 = {𝑢, 𝑣} → 𝑦 = {𝑢, 𝑣})
119, 10eleq12d 2248 . . . . . . . 8 (𝑦 = {𝑢, 𝑣} → ( 𝑦𝑦 {𝑢, 𝑣} ∈ {𝑢, 𝑣}))
128, 11imbi12d 234 . . . . . . 7 (𝑦 = {𝑢, 𝑣} → (((𝑦 ⊆ On ∧ ∃𝑥 𝑥𝑦) → 𝑦𝑦) ↔ (({𝑢, 𝑣} ⊆ On ∧ ∃𝑥 𝑥 ∈ {𝑢, 𝑣}) → {𝑢, 𝑣} ∈ {𝑢, 𝑣})))
13 onintexmid.onint . . . . . . 7 ((𝑦 ⊆ On ∧ ∃𝑥 𝑥𝑦) → 𝑦𝑦)
144, 12, 13vtocl 2793 . . . . . 6 (({𝑢, 𝑣} ⊆ On ∧ ∃𝑥 𝑥 ∈ {𝑢, 𝑣}) → {𝑢, 𝑣} ∈ {𝑢, 𝑣})
151, 3, 14syl2anc 411 . . . . 5 ((𝑢 ∈ On ∧ 𝑣 ∈ On) → {𝑢, 𝑣} ∈ {𝑢, 𝑣})
16 elpri 3617 . . . . 5 ( {𝑢, 𝑣} ∈ {𝑢, 𝑣} → ( {𝑢, 𝑣} = 𝑢 {𝑢, 𝑣} = 𝑣))
1715, 16syl 14 . . . 4 ((𝑢 ∈ On ∧ 𝑣 ∈ On) → ( {𝑢, 𝑣} = 𝑢 {𝑢, 𝑣} = 𝑣))
18 incom 3329 . . . . . . 7 (𝑣𝑢) = (𝑢𝑣)
1918eqeq1i 2185 . . . . . 6 ((𝑣𝑢) = 𝑢 ↔ (𝑢𝑣) = 𝑢)
20 dfss1 3341 . . . . . 6 (𝑢𝑣 ↔ (𝑣𝑢) = 𝑢)
21 vex 2742 . . . . . . . 8 𝑢 ∈ V
22 vex 2742 . . . . . . . 8 𝑣 ∈ V
2321, 22intpr 3878 . . . . . . 7 {𝑢, 𝑣} = (𝑢𝑣)
2423eqeq1i 2185 . . . . . 6 ( {𝑢, 𝑣} = 𝑢 ↔ (𝑢𝑣) = 𝑢)
2519, 20, 243bitr4ri 213 . . . . 5 ( {𝑢, 𝑣} = 𝑢𝑢𝑣)
2623eqeq1i 2185 . . . . . 6 ( {𝑢, 𝑣} = 𝑣 ↔ (𝑢𝑣) = 𝑣)
27 dfss1 3341 . . . . . 6 (𝑣𝑢 ↔ (𝑢𝑣) = 𝑣)
2826, 27bitr4i 187 . . . . 5 ( {𝑢, 𝑣} = 𝑣𝑣𝑢)
2925, 28orbi12i 764 . . . 4 (( {𝑢, 𝑣} = 𝑢 {𝑢, 𝑣} = 𝑣) ↔ (𝑢𝑣𝑣𝑢))
3017, 29sylib 122 . . 3 ((𝑢 ∈ On ∧ 𝑣 ∈ On) → (𝑢𝑣𝑣𝑢))
3130rgen2a 2531 . 2 𝑢 ∈ On ∀𝑣 ∈ On (𝑢𝑣𝑣𝑢)
3231ordtri2or2exmid 4572 1 (𝜑 ∨ ¬ 𝜑)
Colors of variables: wff set class
Syntax hints:  ¬ wn 3  wi 4  wa 104  wo 708   = wceq 1353  wex 1492  wcel 2148  cin 3130  wss 3131  {cpr 3595   cint 3846  Oncon0 4365
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-ia1 106  ax-ia2 107  ax-ia3 108  ax-in1 614  ax-in2 615  ax-io 709  ax-5 1447  ax-7 1448  ax-gen 1449  ax-ie1 1493  ax-ie2 1494  ax-8 1504  ax-10 1505  ax-11 1506  ax-i12 1507  ax-bndl 1509  ax-4 1510  ax-17 1526  ax-i9 1530  ax-ial 1534  ax-i5r 1535  ax-13 2150  ax-14 2151  ax-ext 2159  ax-sep 4123  ax-nul 4131  ax-pow 4176  ax-pr 4211  ax-un 4435  ax-setind 4538
This theorem depends on definitions:  df-bi 117  df-3an 980  df-tru 1356  df-nf 1461  df-sb 1763  df-clab 2164  df-cleq 2170  df-clel 2173  df-nfc 2308  df-ne 2348  df-ral 2460  df-rex 2461  df-rab 2464  df-v 2741  df-dif 3133  df-un 3135  df-in 3137  df-ss 3144  df-nul 3425  df-pw 3579  df-sn 3600  df-pr 3601  df-uni 3812  df-int 3847  df-tr 4104  df-iord 4368  df-on 4370  df-suc 4373
This theorem is referenced by: (None)
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